Method and apparatus for soft buffer management for carrier aggregation

ABSTRACT

An apparatus and a method therein include selecting a size of a soft buffer memory partition per component carrier in a Carrier Aggregation scenario. The method supports multiple carriers to select a size of a soft buffer memory partition, the partition associated with receiving data on at least one component carrier, the multi-carrier system comprising at least two component carriers, each component carrier is associated with a configured bandwidth, the apparatus comprising the processor configured to select a size of a soft buffer memory partition for the first component carrier based at least in part on a first total number of soft channel bits, a first number associated with hybrid automatic retransmit request processes, and the configured bandwidth of the first component carrier.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to wireless communications and,more particularly, to soft buffer partition size determination inwireless terminals in wireless communication systems.

BACKGROUND

Digital data transmissions over wired and wireless links may becorrupted, for instance, by noise in the link or channel, byinterference from other transmissions (e.g., radio transmissions), or byenvironmental factors related to, for example, the speed, direction,location and requests between transmitting and receiving units. Evenwith clear communication channels (i.e., channels with limitedcorruption), which lend themselves to relatively high data rates, it maynot be possible to appropriately decode a data stream with the requisiteerror rates. Digital data transmissions may also be limited by aninability of the receiving or transmitting equipment to appropriatelyencode and decode the data stream at the desired speed with therequisite error rate.

In other situations, it may not be feasible to provide hardware suitablefor high rate data transmission at a cost and portability demanded bythe application. Requested services may range from voice communicationsover high-speed Internet connections to video conferencing. The hardwareat the receiver should be light and use minimal amounts of power inportable applications. Similarly, digital signal processing hardware foraccurate conveyance of data packets should be compact and consume lowpower. Portability restrictions may require that all system attributesbe well designed, using a minimal amount of integrated circuits,electronic components, batteries, and other components.

Error detection and correction codes typically provide mechanismsnecessary to reliably receive and decode data packets. Forward errorcorrection (FEC) codes allow decoders to accurately reconstruct datapackets received with possible errors at the expense of some additionaloverhead (e.g., extra parity bits, extra symbols). Forward errorprotection may protect a data packet. With FEC, the protected datapacket is generally “self-decoding” in that all the data (information)required to reconstruct the data packet is within a single receiveblock. Stored data may rely on FEC for reliable extraction. In two-waysystems, an opportunity for requesting that a data packet beretransmitted upon detection of an error may be available. For example,an automatic repeat or retransmission request (ARQ) may be sent upondetection of an error using, for example, a parity bit check or a cyclicredundancy check (CRC), and then the original data packet may bediscarded. Upon receipt of an ARQ request at the sending station, thepacket may be retransmitted in its original form.

While this simple combination of ARQ and FEC is sometimes called Type IARQ, the term “hybrid ARQ” is usually reserved for a more complexprocedure where a receiver may combine previously received erroneouspackets with a newly received packet in an effort to successfullyascertain the contents of the packet. The general procedure in a hybridautomatic repeat request (HARQ) system is that a receiver may generatean indicator, such as an ARQ request, upon detection of an error in thereceived data packet. Unlike Type I ARQ, the receiver does not discardpreviously received erroneous packets. The receiver may keep (e.g.,store) the entire or portions of the erroneous packet because theerroneous packet may still contain worthwhile information, and thereforethe erroneous packet is not discarded when using HARQ. By combiningerroneous packets, the receiver may be able to assist the FEC to correctthe errors. The receiver may require, however, an abundance of volatilememory for storing previous data packets and provisioning for the needsof the HARQ decoder. A HARQ buffer may contain a large amount of memorydesignated for just this purpose. Large memory requirements,particularly in portable, mobile equipment, may require excessivelylarge space and consume an excessively large amount of power. Managingand optimizing volatile memory available in a communication system isthus desirable.

As demands for higher data rates increase, techniques for inserting moredata into a single or multiple channels become more attractive. Adaptivemodulation and control (AMC) techniques adjust the modulation schemeused for the transmission of data packets. A clear channel, for example,may use a higher order of modulation, e.g., 64-Quadrature AmplitudeModulation (64-QAM), to transmit data at the higher rate. A noisy orpossibly faded and/or interference-limited channel may require the useof a lower order of modulation and consequently a lower data rate. Whenthe channel improves, a high order modulation technique may be usedagain. Multiple input, multiple output (MIMO) transmission techniquesutilizing multiple antennas for transmitting and receivingradio-frequency signals enhance the data rates that are possible usingmultiple channels. Effective HARQ architectures are needed to extractthe full advantages of AMC and MIMO for higher data rates, whileretaining compatibility with ARQ and HARQ systems.

In the 3^(rd) Generation Partnership Project (3GPP) Long Term Evolution(LTE) wireless communications protocol development, a compliant userterminal is typically allocated spectrum resources on a single compliantcarrier in the downlink direction (i.e., from a base station to a userterminal). The uplink spectrum resources for uplink transmissions (i.e.,from the user terminal to the base station) may be on a different singlecompliant carrier for Frequency Division Duplex (FDD) systems or on thesame single compliant carrier for Time Division Duplex (TDD) system. Forsuch a compliant user terminal, there is an expected minimum number ofsoft buffer locations, or a minimum HARQ buffer size that the UE isexpected to provide. The cellular base station may then, based on theHARQ buffer size, be able to determine which codeword bits to the sendto the user. Typically, the base station may determine the amount ofstorage per codeword based on the total number soft buffer locations,the number of HARQ processes and the number of layers for spatialmultiplexing.

It is anticipated that some wireless communications protocols willsupport spectrum aggregation wherein a compliant user terminal, alsoreferred to as user equipment (UE), will be expected to receive data onmultiple component carriers in a single sub-frame. One such protocol isthe 3GPP LTE-Advanced (LTE-A) protocol. Existing control signalingschemes for LTE Release 8 (Rel-8) can be used to allocate resources to aUE on only a single Release 8 compliant carrier. In LTE Rel-8/9, the UEdecides the soft buffer size for each TB (Nir) using the followingformula provided in 3GPP TS 36.212 Rel-8/9 specification:

$\begin{matrix}{N_{IR} = \left\lfloor \frac{N_{{soft}\;}}{K_{MIMO} \cdot {\min \left( {M_{{DL}\; \_ \; {HARQ}},M_{limit}} \right)}} \right\rfloor} & {{Eqn}.\mspace{14mu} (1)}\end{matrix}$

where N_(soft) is the total number of soft channel bits (from Table4.4-1 in TS 36.306), K_(MIMO) is equal to 2 if the UE is configured toreceive PDSCH transmissions based on spatial multiplexing with rankgreater than 1 such as transmission modes 3, 4 or 8, 1 otherwise, M_(DL)_(—) _(HARQ) is the maximum number of DL HARQ processes (i.e., HARQprocesses in the downlink direction), and M_(limit) is a constant equalto 8. For TDD, when the number of DL HARQ processes exceeds 8,techniques such as soft buffer overbooking, equal soft buffer splitbetween HARQ processes, and/or other statistical buffer managementtechniques are applied. For Rel-10 with Carrier Aggregation (CA), new UEcategories with support for 2 Component Carriers (CCs) need to bedefined. Other UE categories with support for larger number of CCs maybe defined for later releases. The bandwidth (BW) of individualaggregated CCs can be same or different (e.g., 10 MHz+10 MHz, 15 MHz+5MHz etc.).

For LTE Release 10 with CA, new UE categories with support for 2component carriers are yet to be defined. Also, other UE categories withsupport for larger numbers of component carriers may be defined forlater releases. The bandwidth of the individual aggregated componentcarriers can be same or different (e.g. 10 MHz+10 MHz, 15 MHz+5 MHzetc.). Thus, there is a need for a soft buffer management wherein the UEmay receive downlink transmissions from the eNB (or a plurality of eNBs)on one or more of the multiple component carriers.

The various aspects, features and advantages of the invention willbecome more fully apparent to those having ordinary skill in the artupon careful consideration of the following Detailed Description thereofwith the accompanying drawings described below. The drawings may havebeen simplified for clarity and are not necessarily drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system.

FIG. 2 illustrates a schematic block diagram of a user terminal.

FIG. 3 is a process flow diagram of a first embodiment.

FIG. 4 is a process flow diagram of a second embodiment.

DETAILED DESCRIPTION

In FIG. 1, a multi-carrier wireless communication system 100 comprisesone or more fixed base infrastructure units 101, 102 forming a networkdistributed over a geographical region for serving remote units in thetime and/or frequency domain. A base unit may also be referred to as anaccess point, access terminal, base, base station, Node-B, eNode-B, arelay node, or by other terminology used in the art. The one or morebase units each comprise one or more transmitters for downlinktransmissions and one or more receivers for receiving uplinktransmissions. The base units are generally part of a radio accessnetwork that includes one or more controllers communicably coupled toone or more corresponding base units. The access network is generallycommunicably coupled to one or more core networks, which may be coupledto other networks, like the Internet and public switched telephonenetworks, among other networks. These and other elements of access andcore networks are not illustrated but they are well known generally bythose having ordinary skill in the art.

In FIG. 1, the one or more base units serve a number of remote units103, 104 within a corresponding serving area, for example, a cell or acell sector via a wireless communication link. The remote units may befixed units or mobile terminals. The remote units may also be referredto as subscriber units, mobiles, mobile stations, users, terminals,subscriber stations, user equipment (UE), user terminals, relays, or byother terminology used in the art. The remote units also comprise one ormore transmitters and one or more receivers. In FIG. 1, the base unit101 transmits downlink communication signals to serve remote unit 103 inthe time and/or frequency and/or spatial and/or code domain. The remoteunit 103 communicates directly with base unit 101 via uplinkcommunication signals. A remote unit 104 communicates directly with baseunit 102. In some cases the remote unit may communicate with the baseunit indirectly through an intermediate relay node.

In one implementation, the wireless communication system is compliantwith the 3GPP Universal Mobile Telecommunications System (UMTS) LTEprotocol, also referred to as EUTRA or Release-8 (Rel-8) 3GPP LTE orsome later generation thereof, wherein the base unit transmits using anorthogonal frequency division multiplexing (OFDM) modulation scheme onthe downlink and the user terminals transmit on the uplink using asingle carrier frequency division multiple access (SC-FDMA) scheme, or adiscrete Fourier Transform spread OFDM (DFT-SOFDM). More generally,however, the wireless communication system may implement some other openor proprietary communication protocol, for example, WiMAX, among otherprotocols. The disclosure is not intended to be limited to theimplementation of any particular wireless communication systemarchitecture or protocol.

In FIG. 2, a UE 200 comprises a controller/processor 210 communicablycoupled to memory 212, a database 214, a transceiver 216, input/output(I/O) device interface 218 via a system bus 220. The UE is compliantwith the protocol of the wireless communication system within which itoperates, for example, the 3GPP LTE Rel-8 or later generation protocoldiscussed above. In FIG. 2, the controller/processor 210 may beimplemented as any programmed processor. However, the functionalitydescribed herein may also be implemented on a general-purpose or aspecial purpose computer, a programmed microprocessor ormicrocontroller, peripheral integrated circuit elements, anapplication-specific integrated circuit (ASIC) or other integratedcircuits, hardware/electronic logic circuits, such as a discrete elementcircuit, a programmable logic device, such as a programmable logicarray, field programmable gate-array, or the like. In FIG. 2, the memory212 may include volatile and nonvolatile data storage, including one ormore electrical, magnetic or optical memories such as a random accessmemory (RAM), cache, hard drive, read-only memory (ROM), firmware, orother memory device. The memory may have a cache to speed access tospecific data. Data may be stored in the memory or in a separatedatabase. The memory may be embedded with an ASIC that may include thebaseband processor. Such memory is sometimes referred to as on-chipmemory. Alternatively, the memory may be shared with other processors inthe device such as an application or graphics processor, in which casethe memory may be referred to as off-chip memory. The transceiver 216 iscapable of communicating with user terminals and base stations pursuantto the wireless communication protocol implemented. The I/O deviceinterface 218 connects to one or more input devices that may include akeyboard, mouse, pen-operated touch screen or monitor, voice-recognitiondevice, or any other device that accepts input. The I/O device interfacemay also connect to one or more output devices, such as a monitor,printer, disk drive, speakers, or any other device provided to outputdata.

A wireless communication device in the multi-carrier network generallysupports multiple carriers comprising at least two component carriers,wherein each component carrier is associated with a configuredbandwidth. For example, a first component carrier may be associated witha first bandwidth and a second component carrier may be associated witha second bandwidth, and so on. The component carrier may be a downlinkcomponent carrier or an uplink component carrier in the case of FDD orsupport both downlink and uplink in the case of TDD. The downlinkcomponent carrier and uplink component carrier may have the same ordifferent bandwidth. In one embodiment, the first configured bandwidthof the first component carrier is not equal to the second configuredbandwidth of the second component carrier. For instance, the firstcomponent carrier bandwidth may be 15 MHz, while the second componentcarrier may be 5 MHz, leading to an aggregate bandwidth of 20 MHz. Inanother embodiment, the first configured bandwidth of the firstcomponent carrier is equal to the second configured bandwidth of thesecond component carrier. For instance, the first and second componentcarriers have an equal bandwidth of 10 MHz each, leading to an aggregatebandwidth of 20 MHz.

The wireless communication device can receive data transmissions onmultiple component carriers using multiple serving cells with eachserving cell associated with a particular component carrier of aparticular bandwidth. The wireless communication device can indicate tothe network the number of component carriers it supports using RadioResource Configuration (RRC) signaling. Alternately, the wirelesscommunication device can also indicate to the network via RRC signaling,the number of component carriers it can support and the number ofspatial layers (i.e., the number of TBs that the device can receive viaspatial multiplexing) it can support for each component carrier or thetotal number of spatial layers over all the component carriers itsupports or a subset of the supported component carriers.

In one embodiment, a soft buffer size for LTE Release 10 (Rel-10) UEcategories is specified in a specification document such as a 3GPPTechnical Specification based on the cumulative aggregated bandwidth.This allows for defining fewer UE categories based on maximum possibledata rate handled by the UE. An example is described below withreference to Table 1. According to this embodiment, computation of softbuffer size for each TB for each component carrier can be done byintroducing component carrier related variables into Equation (1).

Consider the example of Category (Cat) 6 in Table 1. This UE category isbased on LTE Rel-8/9 Cat3 but with carrier aggregation (CA) support for2 component carriers. The peak data rate handled by cat6 is same as cat3(i.e., ˜100 Mbps) but cat6 can achieve the peak data rate by receivingon either one CC with 20 MHz bandwidth or on two CCs whose aggregatebandwidth is 20 MHz. Cat6 can be useful for deployments where spectrumis available in two separate 10 MHz portions in different bands (e.g.,Band 13 and Band 1 as specified in the 3GPP specification) or inHeterogeneous network deployments (comprising base stations of differentclasses/characteristic/coverage features such as macro eNBs, femtocells, pico cells, relay cells, etc) where the available bandwidth issplit into to 2 CCs (or a plurality of CCs in general) for the purposeof interference management or load sharing or resource sharing.

TABLE 1 Rel-10 UE categories (based on aggregated bandwidthconfiguration) Maximum Maximum Maximum number number number of of DL- ofbits of supported SCH TB a DL-SCH Total layers bits TB Number forMaximum received received of soft spatial number UE within a within achannel multiplexing of CCs Category TTI TTI bits in DL supportedComments Category 1 10296 10296 250368 1 — Rel8/9 Category 2 51024 510241237248 2 — Rel8/9 Category 3 102048 75376 1237248 2 — Rel8/9 Category 4150752 75376 1827072 2 — Rel8/9 Category 5 299552 149776 3667200 4 —Rel8/9 Category 6 102043 75376 1237248 2 2 Rel10 (20 MHz, any BWcombination) Category 7 299552 75376 3667200 2 2 Rel10 (40 MHz any BWconfiguration)

According to one aspect of the disclosure, the processor of the wirelesscommunication device that supports multiple carriers, for example, thetransceiver 216 in FIG. 2, is configured to determine a size of a softbuffer memory partition of the memory element for a first componentcarrier. In one embodiment, the soft memory buffer size is determinedbased on a first configured bandwidth of the first component carrier anda second configured bandwidth of a second component carrier. The processflow diagram 300 of FIG. 3 schematically illustrates this portion of theprocess at 310. The processor is also configured to control thereceiver, for example, the transceiver 216 in FIG. 2, to receive data onthe first component carrier based on the size of the soft buffer memorypartition, as illustrated at 320 in FIG. 3.

In one implementation, the processor is configured to determine the sizeof the soft buffer memory partition based on a total number of softchannel bits. In one specific embodiment, the total number of softchannel bits is determined based on a category of the wirelesscommunication device. For instance, the UE category 6, the total numberof soft channel bits is 1237248 bits. In another embodiment, the totalnumber of soft channel bits is determined based on a first numberassociated with HARQ processes determined based at least in part onduplex mode. For instance, for the FDD system, the first numberassociated with the HARQ processes may be fixed to 8, corresponding toeight HARQ processes support in LTE FDD Rel-8 for some transmissionmodes (i.e., configured to transmit a maximum of single TB per TTI),whereas it may be 8 or 16 for other transmission modes (i.e., configuredto transmit a maximum of 2 TBs per TTI). In future releases, the numbermay be different because of future HARQ optimization (such as furtherreduced latency leading to smaller HARQ Round Trip Times (RTT) such asfrom 8 ms in Rel-8 to e.g., 4 ms, smaller TTIs such as 0.5 ms, furtherfast ACK feedback mechanisms such as HARQ feedback is transmitted within2 ms instead of 4 ms as in Rel-8, etc). In a TDD system, the number maybe dependent upon the uplink/downlink configuration or the configurationof the uplink and downlink subframes with one or more radio frames. Inone example, for a downlink subframe heavy configuration wherein thereare more downlink subframes than uplink subframes, the number may be ashigh as 15 HARQ processes in the DL subframe, while in UL heavysubframes (more UL than DL subframes), the number be as low as 4. Inanother embodiment, the total number of soft channel bits is determinedbased on a maximum number of TBs transmittable to the wirelesscommunication device in one transmission time interval (TTI). Themaximum number of TBs within a TTI can vary based on the transmissionmode and/or transmission rank with each component carrier. In anotherembodiment, the processor is configured to determine the total number ofsoft channel bits based on a second number associated with HARQprocesses determined based at least in part on a number of MultipleInput Multiple Output (MIMO) streams. For instance, if the number ofMIMO streams is two or more, it may allow more than one TB to betransmitted with the TTI to the UE. In that case, the total number ofsoft channel bits may be doubled.

In another embodiment, the first component carrier supports some maximumnumber of spatial multiplexing layers and the processor determines thesize of the soft buffer memory partition based on the maximum number ofspatial multiplexing layers supported on the first component carrier.

In another embodiment, a ratio of the size of the soft buffer memorypartition for the first component carrier and a size of the soft buffermemory partition for the second component carrier is substantially equalto a ratio of the first configured bandwidth of the first componentcarrier and the second configured bandwidth of the second componentcarrier. Thus, if a first component carrier has a bandwidth that islarger than a second component carrier, then the first component carriermay be assigned a proportionally greater soft buffer allocation comparedto the second component carrier. This can result in uneven memorypartitioning among the component carriers. The processor may alsodetermine the size of the soft buffer memory partition based on abandwidth corresponding to a signaled category of the wirelesscommunication device.

With reference to Table 1 above, soft buffer dimensioning for UE Cat3 inLTE Rel-8/9 was defined assuming Limited Buffer Rate Matching (LBRM).With LBRM, for a subset of large TB sizes, the UE is allowed toprovision a per TB soft buffer size that is smaller than the maximumrequired soft buffer size to achieve mother code rate of 1/3. Forexample, a LTE cat3 UE operating with 2 spatial layers must support alargest TB size of 75376. For this TB size, given 1237248 total softchannel bits (i.e., soft buffer size corresponding to these bits), theUE can only provision 77328 soft channel bits per each of the twopossible TBs within a TTI (number of TBs within a TTI may vary with thetransmission mode or transmission rank and/or based on the controlsignaling from the eNB). This amounts to an effective mother code rate(ECR) or minimum achievable code rate of around 0.97 for the largestpossible TB size. The effective mother code rate may be defined as thenumber of information bits divided by the number of encoded bits thatcan be stored in the soft buffer. Note that the effective mother coderate may be different from the code rate employed by the FEC encodersuch as the turbo code rate, as the two are defined from differentperspectives. It is possible to have a turbo code (FEC encoder) coderate of 1/3, wherein the code is shortened or some of the output paritybits are deleted (due to soft buffer storage limitations) to lead to aneffective mother code rate larger than 1/3. For instance, if 50% of theoutput parity bits are punctured, then the ECR is approximately 2/3whereas the turbo code rate is 1/3. If the mother code rate (oreffective mother code rate) is greater than 1, then the amount of softbuffer storage is likely insufficient as all information bits may not berecoverable. The ECR is reduced for smaller TB sizes. For TB sizes lessthan 25456 approximately, the ECR is the same as mother code rate of1/3, which means that LBRM need not be employed.

It is expected that Limited Buffer Rate Matching (LBRM) will also beadopted in LTE Rel-10, especially if the Rel-10 UE Categories arealigned with Rel-8 UE categories in terms of a peak data rate and otherattributes such as DL TBS per TTI and DL TBS per CW (e.g., UE Cat6 inTable 1). Assuming that only one soft buffer size is specified on atotal aggregated bandwidth, the computation of per TB soft buffer sizeat the UE for each CC can be handled by the Rel-10 specifications (e.g.,in 3GPP TS 3GPP TS 36.212) with the following options.

According to a first option, the soft buffer size that the UE mustprovision per CC is semi-statically configured by the eNodeB usingdedicated RRC signaling. The RRC signaling can be the explicit signalingof a number of soft channel bits provisioned per CC or the signaling ofper CC scaling factors that scale the total number of soft channel bits(obtained from a Table in TS 36.306 or another 3GPP specification) foreach CC. Here, the soft buffer size per CC may be determined as apercentage or a fraction of the total soft buffer and this percentage issignalled using x bits, wherein x>=1. For instance if x=2, thenpotentially, the four states designated by the two bits indicate thesoft buffer percentage for the corresponding CC such as 25%, 50%, 75%and 100%, respectively. It is also possible to jointly signal the softbuffer size for the CC with other configuration parameters within theRRC signaling used for configuration of the CC.

With reference to Equation (1) above, if N_(soft) is total soft buffer(determined by the UE from the Table in 36.306) and SBPCC1 and SBPCC2are the two CC-specific percentages or scaling factors signaled in theRRC (or in a higher-layer message or a downlink message) or specified ina communications protocol, then the soft buffer allocated to CC1 isN_(soft,CC1)=└SBP_(CC1)·N_(soft) ┘. The remaining soft buffer can beassigned to the second CC N_(soft,CC2)=N_(soft)−N_(soft,CC1) or similarformula as above can be used for CC2.

Within a CC (e.g., CC1), the soft buffer size for each TB (Nir_CCx) canbe computed using a formula similar to Equation 1 but with Nsoft,K_MIMO, M_DL_HARQ replaced by Nsoft_CCx, K_MIMO_CCx, M_DL_HARQ CCxrespectively. Therefore soft buffer size for each TB received on CC1(N_IR,CC1) can be computed using the formula

$\begin{matrix}{N_{{IR},{{cc}\; 1}} = \left\lfloor \frac{N_{{soft},{{CC}\; 1}}}{K_{{MIMO},{{CC}\; 1}} \cdot {\min \left( {M_{{{DL}\; \_ \; {HARQ}},{{CC}\; 1}},M_{limit}} \right)}} \right\rfloor} & {{Eqn}.\mspace{14mu} (2)}\end{matrix}$

where N_soft,CC1 is the portion of the total soft buffer (N_soft)partitioned for CC1, K_MIMO_CC1 is a number dependent on the number ofspatial multiplexing layers supported in CC1, and M_DL_HARQ,CC1 is equalto the number of HARQ processes supported on CC1. The formula given inEquation 2 is reused for all the other component carriers (e.g., byreplacing CC1 with CC2 when two component carriers are used) to computesoft buffer size for TBs received on those component carriers. Althoughit is possible to make the value M_limit different for each aggregatedcomponent carrier to obtain even more flexibility in soft bufferpartitioning, maintaining a constant M_limit value across all componentcarriers is desirable from an implementation simplicity perspective.

The formula in Equation 2 splits the soft buffer partitioned for aparticular CC (N_soft,CCx) into K_MIMO,CCx*M_DL_HARQ,CCx equal sizepartitions where M_DL_HARQ,CCx is equal to the number of HARQ processessupported on CCx and K_MIMO_CC1 is a number dependent on the number ofspatial multiplexing layers supported in CCx. For example, whenM_DL_HARQ,CCx=8, there can 8 equal sized partitions, when K_MIMO,CCx=1and 16 equal sized partitions (one per codeword or per transport block)in case of MIMO where K_MIMO,CCx=2. Alternatively, within each CC, thesoft buffer may be split unevenly among the HARQ processes for the caseswhere some HARQ processes require small HARQ memory or soft buffer. Forinstance, small VoIP packets via semi-persistent scheduling (SPS) mayrequire smaller soft buffer memory due to smaller packet sizes (or TBsizes) compared to other HARQ processes that may be serving filedownloads or larger packet sizes. It is also possible to prioritize HARQprocesses based on Quality of Service (QoS) or other considerationswhere in a higher priority HARQ process is assigned a larger soft bufferpartition and second priority HARQ process is assigned a second smallersoft buffer partition.

According to a second option, for two DL CCs, the soft buffer for LTERel-10 can be split equally between the two DL CCs without explicitlyrelying on RRC signaling for the soft buffer partition information. Inthis case SBPCC1=0.5 and SBPCC2=0.5. This option is especially suitablewhen the bandwidth of aggregated CCs is substantially equal (e.g., ifCC1=10 MHz, and CC2=10 MHz). More generally, if P component carriers areused then soft buffer per CC can be computed as

$\begin{matrix}{N_{{soft},{{CC}\; 1}} = {\left\lfloor \frac{N_{soft}}{P} \right\rfloor.}} & {{Eqn}.\mspace{14mu} (3)}\end{matrix}$

Herein, the P component carriers correspond to the configured oractivated component carriers. Alternately, P can be the number ofcomponent carriers supported by the UE and this number can be indicatedby the UE to the base station as part of UE capability signaling. Asmentioned previously, the remaining soft buffer locations after thepartition using the floor function may be allocated to one of thecomponent carriers (preferably the anchor carrier or the primarycomponent carrier). An anchor or the primary component carrier may bedefined as the carrier over which the UE receives synchronizationsignals, system information messages, and/or paging messages, etc. Itmay also be defined as the component carrier on which the UE performsRadio Resource Management (RRM) measurement and/or monitors the PDCCH.It is also noted that a ceil or round function may be used instead ofthe floor for some component carriers. Floor(x) is the largest integersmaller than or equal to x. Ceil (x) is the smallest integer larger thanor equal to x.

According to a third option, for two DL CCs, the soft buffer for LTERel-10 can be split unequally between the two DL CCs without explicitlyrelying on RRC signaling for the soft buffer partition information. Theimplicit partitioning can be based on bandwidth or on a number ofresource block (RBs) of each aggregated CC. With this option, if Nsoftis total soft buffer and BW_(CC1) and BW_(CC2) are the two CCbandwidths, then the soft buffer allocated to CC1 is

$\begin{matrix}{N_{{soft},{{CC}\; 1}} = \left\lfloor {\left( \frac{{BW}_{{CC}\; 1}}{{BW}_{{CC}\; 1} + {BW}_{{CC}\; 2}} \right)N_{soft}} \right\rfloor} & {{Eqn}.\mspace{14mu} (4)}\end{matrix}$

The remaining soft buffer can be assigned to the second CC

N _(soft,CC2) =N _(soft) −N _(soft,CC1)  Eqn (5).

Instead of Floor ( ), the Ceil( ), or Round( ), functions can be usedalternatively. Also, a similar formula can be used for CC2 soft bufferdetermination:

$\begin{matrix}{N_{{soft},{{CC}\; 2}} = {\left\lfloor {\left( \frac{{BW}_{{CC}\; 2}}{{BW}_{{CC}\; 1} + {BW}_{{CC}\; 2}} \right)N_{soft}} \right\rfloor.}} & {{Eqn}.\mspace{11mu} (6)}\end{matrix}$

Alternatively, implicit partitioning can be based on a maximum sum ofTBS that is allowed on each CC. With this option, if Nsoft is total softbuffer and if TBS_(CC1) and TBS_(CC2) are the max sum of TBS per CC1 perTTI and max sum of TBS per CC2 per TTI, then the soft buffer allocatedto CC1 is

$\begin{matrix}{N_{{soft},{{CC}\; 1}} = {\left\lfloor {\left( \frac{{TBS}_{{CC}\; 1}}{{TBS}_{{CC}\; 1} + {TBS}_{{{CC}\; 2}\;}} \right)N_{soft}} \right\rfloor..}} & {{Eqn}.\mspace{14mu} (7)}\end{matrix}$

The same formula can be extended to the case of an arbitrary number ofaggregated CCs including three component carriers, four componentcarriers, and five component carriers.

The remaining soft buffer can be assigned to the second CC as

$\begin{matrix}{N_{{soft},{{CC}\; 2}} = {N_{soft} - {N_{{soft},{{CC}\; 1}}.}}} & {{Eqn}\mspace{14mu} (8)} \\{N_{{soft},{CCj}} = {\left\lfloor {\left( \frac{{TBS}_{CCj}}{\sum\limits_{i = 0}^{C - 1}{TBS}_{{CC}\; i}} \right)N_{soft}} \right\rfloor.}} & {{Eqn}\mspace{14mu} (9)}\end{matrix}$

where N_(soft,CCj) indicates the soft buffer size for component carrierj, wherein the TBS_(CCi) is the maximum TBS sum, i,j=0, 1, 2 . . . C−1and wherein C is the number of component carriers.

In this case, the maximum data rate achievable by the UE in each CC iscapped according to the max sum of TBS per CC (i.e., the maximum numberof TB bits within a TTI per CC). For instance, in one example, the 100Mbps target is achievable by allowing max TBS sum of 75376 on CC1, and36214 on CC2. Thus, the maximum data rate achievable by the UE on CC1may only be 75 Mbps, while the remaining 25 Mbps has to be achieved byusing CC2. The maximum TBS that is allowed on each CC can be determinedby the UE based on per CC bandwidth (or number of RBs) for instance fora 50-RB max allocatable bandwidth, the max TBS may be determined bylooking up the TBS/MCS table corresponding to 50 RBs and MCS=26 (largestMCS) in 36.213. Alternatively, the maximum sum of TBS that is allowed oneach CC can be specified in the UE category Table in 36.306. Similarlythe maximum TBS that is allowed on each CC can be specified in the UEcategory Table in 36.306. Alternatively, the maximum sum of TBS that isallowed on each CC can be signaled to the UE using RRC signaling, as inthe first option described above. Similarly, the maximum TBS that isallowed on each CC can be signaled to the UE using RRC signaling, as inthe first option.

Table 2 shows the LTE Rel-10 UE categories (based on aggregatedbandwidth configuration). The following parameters may be pre-specifiedin TS36.306 or these parameters may be signaled as part of the RRC orother higher layer signaling: Maximum number of DL-SCH TB bits receivedwithin a TTI for CC1; Maximum number of bits of a DL-SCH TB receivedwithin a TTI for CC2; Maximum number of a DL-SCH TB bits received withina TTI for CC1; and Maximum number of bits of a DL-SCH TB received withina TTI for CC2.

TABLE 2 Maximum Maxi- Maximum Maximum number mum number Maximum Maximumnumber of number of Maximum number number of bits of of bits of numberof of DL- a DL- DL- a DL- of bits of supported SCH SCH SCH SCH DL- a DL-Total layers TB bits TB TB bits TB SCH SCH Number for received receivedreceived received TB bits TB of spatial Maximum within within withinwithin received received soft multiplexing number a TTI a TTI a TTI aTTI UE within within channel in of CCs For For For For Category a TTI aTTI bits DL supported CC1 CC1 CC2 CC2 Comments Category 1 10296 10296250368 1 — — — — — Rel8/9 Category 2 51024 51024 1237248 2 — — — — —Rel8/9 Category 3 102048 75376 1237248 2 — — — — — Rel8/9 Category 4150752 75376 1827072 2 — — — — — Rel8/9 Category 5 299552 149776 36672004 — — — — — Rel8/9 Category 6 102048 75376 1237248 2 2 75376 75376 2537625376 Rel10 (20 MHz, any BW combination) Category 7 299552 75376 36672002 2 149776 75376 149776 75376 Rel10 (40 MHz any BW configuration)

Alternately, implicit partitioning can be based on maximum TBS that isallowed on each CC and considering the number of spatial layerssupported on each CC. With this option, if Nsoft is total soft bufferand if TBS_(CC1) and TBS_(CC2) are the max of TBS per CC1 per TTI andmax of TBS per CC2 per TTI, and K_(MIMO,CC1) and K_(MIMO,CC2) are theK_(MIMO) values for CC1 and CC2, respectively, then the soft bufferallocated to CC1 is

$\begin{matrix}{N_{{soft},{{CC}\; 1}} = {\left\lfloor {\left( \frac{K_{{MIMO},{{CC}\; 1}} \cdot {TBS}_{{CC}\; 1}}{{K_{{MIMO},{{CC}\; 1}} \cdot {TBS}_{{CC}\; 1}} + {K_{{MIMO},{{CC}\; 2}} \cdot {TBS}_{{CC}\; 2}}} \right)N_{soft}} \right\rfloor.}} & {{Eqn}.\mspace{14mu} (10)}\end{matrix}$

The remaining soft buffer can be assigned to the second CC

N _(soft,CC2) =N _(soft) −N _(soft,CC1)  Eqn. (11).

In this case, the soft buffer is reconfigured every time any of thevariables in the equation change, i.e., whenever an RRC message oranother message (e.g., sent on a PDCCH) reconfigures the transmissionmodes on either CC, etc.

Alternatively, implicit partitioning can be based on the CC bandwidth(in MHz or number of RBs) and considering the number of spatial layerssupported on each CC:

$\begin{matrix}{N_{{soft},{{CC}\; 1}} = \left\lfloor {\left( \frac{K_{{MIMO},{{CC}\; 1}} \cdot {BW}_{{CC}\; 1}}{{K_{{MIMO},{{CC}\; 1}} \cdot {BW}_{{CC}\; 1}} + {K_{{MIMO},{{CC}\; 2}} \cdot {BW}_{{CC}\; 2}}} \right)N_{soft}} \right\rfloor} & {{Eqn}.\mspace{14mu} (12)}\end{matrix}$

with the remaining soft buffer can be assigned to the second CC

N _(soft,CC2) =N _(soft) −N _(soft,CC1)  Eqn. (13).

To maximize the achievable data rate within a component carrier denotedas CCx, the maximum number of DL-SCH TB bits received within a TTI for aCCx can be set to the less than or equal to the soft buffer size for aTB on CCx (N_(IR,CCx)) times the number of spatial layers supported(K_(MIMO,CCx)). It is further limited by the maximum number of DL-SCH TBbits received within a TTI for the aggregated BW. For example, for CC1BW=15 MHz and CC2 BW=5 MHz, total soft buffer size=1237248 bits,K_(MIMO,CC1)=2, K_(MIMO,CC2)=2, the soft buffer sizes for each CC isN_(soft,CC1)=927936, and N_(soft,CC2)=18336. The maximum number ofDL-SCH TB bits received within a TTI for CC1 and CC2 is 93776 and 36672,respectively, and is less than or equal to the maximum number of DL-SCHTB bits received within a TTI for the aggregated bandwidth which is102048 bits. The maximum number of bits of a DL-SCH TB received within aTTI for CC1 and CC2 is approximately 55056 and 18336 bits respectivelycorresponding to the maximum TBS size for the respective CC BW. In anyTTI, the sum of the number of DL-SCH TB bits received within a TTI onboth CC1 and CC2 is limited by the maximum number of DL-SCH TB bitsreceived within a TTI for the aggregated bandwidth (102048 bits).

For two DL CCs, the soft buffer for LTE Rel-10 can be split unequallybetween the two DL CCs without explicitly relying on RRC signaling forthe soft buffer partition information.

While the above options were shown only for two component carriers, itis understood that same technique can be applied to any number ofcomponent carriers. For example with J component Carriers with the j-thcomponent carrier having a bandwidth BWCC,j, the size of soft bufferpartition may be determined as follows.

$\begin{matrix}{N_{{soft},{CC},j} = {\left\lfloor {\left( \frac{{BW}_{{CC},j}}{\sum\limits_{i = 1}^{J}B_{{CC},i}} \right)N_{soft}} \right\rfloor.}} & {{Eqn}.\mspace{14mu} (14)}\end{matrix}$

Generally a multi-carrier network may change an activation orconfiguration of the component carriers. Such a change may be made by abase station scheduler or network controller entity. In someembodiments, a UE that supports multiple carriers reconfigures softbuffer provisioning during configuration and/or removal of additionalcomponent carriers. The soft buffer provisioning can also bereconfigured whenever additional component carriers are activated orde-activated. For example, the UE may re-determine the size of the softbuffer memory partition for one component carrier in response to achange in activation or a change in a configuration of the samecomponent carrier. The UE may also re-determine the size of the softbuffer memory partition for one component carrier in response to achange in activation or a change in a configuration of another componentcarrier. Typically, the configuration and activation of a componentcarrier may have subtle differences. For instance, a component carriermay be configured and de-configured on a slower scale compared to anactivation/deactivation that may occur more frequently. Theactivation/deactivation may be considered as providing a similar featuresuch as non-DRX/DRX (discontinuous reception) in the single componentcarrier case. A UE may be configured for multiple component carriers butthe component carriers may be activated and deactivated more frequently.A de-configured component carrier is deactivated, but a deactivatedcomponent carrier may still remain to be a configured component carrier.The serving cell may choose to re-configure the UE to support adifferent set of component carriers not including the deactivatedcomponent carrier.

In some instances however this may result in soft buffer configurationchanges that are too frequent, which is undesirable. To alleviate thisproblem, the base station or eNodeB can signal whether or not the UEshould reset its soft buffers for all component carriers. This signalingcan comprise one or more bits or codepoints. For example, the signalingcould occur in RRC configuration messages that that configure/removeadditional component carriers. It could also occur in separate RRCmessages, or in Medium Access Control-Control Elements (MAC-CEs) thatactivate/deactivate additional component carriers.

For a given HARQ process x on CC1, if a scheduled transport block size(TBS) exceeds a effective mother code rate of 1 due to insufficient softbuffer allocation, then the HARQ process x on CC1 can borrow a portionof or the entire soft buffer allocated to HARQ process x from CC2. Inthe latter case, the TB on the HARQ process x from CC2 is terminated.This approach allows the UE to achieve peak data rates using just oneCC. For instance, this can be done by specifying a max sum TBS per HARQprocess.

According to one aspect of the disclosure, the processor of the wirelesscommunication device that supports multiple carriers, for example, thetransceiver 216 in FIG. 2, is configured to determine a number of softchannel bits associated with the first component carrier based on thereceived signal. The process flow diagram 400 of FIG. 4 schematicallyillustrates this portion of the process at 410. In one embodiment, thesignal indicates either the number of soft channel bits associated withthe first component carrier or a fraction of a total number of softchannel bits associated with the first component carrier. The wirelesscommunication device may thus determine the number of soft channel bitsby either obtaining the number directly from the received signal or byperforming a computation based on the fractional information provided inthe received signal. The received signal is selected from a groupcomprising: a radio resource control (RRC) message, a carrier activationmessage, and a carrier configuration message.

The processor is also configured to determine a size of a soft buffermemory partition for a HARQ process associated with the first componentcarrier based on the determined number of soft channel bits associatedwith the first component carrier and based on a first number associatedwith the HARQ process associated with the first component carrier. Thisportion of the process is illustrated at 420 in FIG. 4. In oneembodiment, the size of the soft buffer memory partition is based on asecond number associated with the HARQ process associated with the firstcomponent carrier. In another embodiment, the size of the soft buffermemory partition is determined based on a first number associated withthe HARQ process, wherein the first number comprises a maximum number ofdownlink HARQ processes on the first component carrier. In anotherembodiment, the size of the soft buffer memory partition is determinedbased on a second number associated with HARQ processes, wherein thesecond number comprises a configured maximum number of HARQ processes onthe second component carrier.

In some embodiments, the wireless communication device supportingmultiple carriers determines a size of a soft buffer memory partitionfor a first component carrier based on the received signal. The devicealso determines a size of a soft buffer memory partition for a HARQprocess associated with the first component carrier. The size of thesoft buffer memory partition for the HARQ process is based on the numberof soft channel bits associated with the first component carrier andbased on a first number associated with a HARQ process of the firstcomponent carrier. As described above, the signal indicates either thenumber of soft channel bits associated with the first component carrieror a fraction of a total number of soft channel bits associated with thefirst component carrier. The wireless communication device may thusdetermine the number of soft channel bits by either obtaining the numberdirectly from the received signal or by computation based on thefractional information provided in the received signal. The receivedsignal may be embodied as RRC message, or as a carrier activationmessage, or as a carrier configuration message.

In another embodiment, the wireless communication device supportingmultiple carriers selects or determines a size of a soft buffer memorypartition for a first component carrier based on a first maximum numberof downlink shared channel (DL-SCH) TB bits received within a TTIassociated with the first component carrier and a first maximum numberof DL-SCH TB bits received within a TTI associated with a secondcomponent carrier. In an alternative embodiment, the size of the softbuffer memory partition for the first component carrier is determinedbased on a second maximum number of bits of a DL-SCH TB received withina TTI associated with the second component carrier and a second maximumnumber of bits of DL-SCH TB bits received within a TTI associated withthe second component carrier.

The soft buffer partition determination is a part of the FEC and HARQprocessing in many modern systems, such as LTE Rel-8 and Rel-10 andevolved systems that employ advanced coding techniques such as turbocoding, low-density parity check coding, convolutional coding,Reed-Solomon coding, Reed-Muller coding, etc. If the system uses HARQprocessing, then multiple transmissions may be needed for a giveninformation block, and the rate matching algorithm may be required toprovide different versions of the codeword (e.g., for incrementalredundancy HARQ).

Typically, in LTE Rel-8 and advanced systems, if the input informationblock (e.g., TB or concatenated TB) to the turbo coder (or the channelencoder) is larger than the maximum size supported by the turbointerleaver (such as based on a Quadratic Permutation Polynomial (QPP)),then the TB is segmented into multiple code block segments or codeblocks, each of which is individually turbo-encoded and rate-matched,thus allowing an efficient pipelined operation. Typically, thesegmentation procedure may also involve the attachment of Code Block(CB) and/or TB level CRC to facilitate error detection. Some of therelevant details are described in this document, but detailed TBprocessing including CRC coding, turbo coding with tail bits ortail-biting and tail bits handling in the rate matching procedure isomitted here since it is well known to those of ordinary skill in theart.

In LTE Rel-8 with data channel utilizing turbo coding of the code blocksegments, the rate matching method comprises receiving systematic bits(typically corresponding to the information bits comprising the codeblock and optionally CRC bits and filler bits), a first block of paritybits, and a second block of parity bits (and in general any block ofencoded parity bits, but not necessarily limited to systematic bits).The systematic bits, the first block of parity bits, and the secondblock of parity bits may comprise, dummy bits, tail bits and/or fillerbits. The systematic bits, first block of parity bits, and second blockof parity bits are individually block interleaved and the first block ofparity bits are interlaced with the second block of parity bits tocreate interlaced parity bits. The interleaved systematic bits arepre-pended to the interlaced parity bits to create a circular buffer andredundancy versions are defined to start in particular positions of thecircular buffer. When a redundancy version (RV) and a number of desiredbits are received, the number of desired bits are output starting at theRV bit position, and taking a desired block of consecutive bits from thecircular buffer (wrapped around to the beginning if the last bit of thecircular buffer is reached). Different codeword versions for HARQoperation are obtained by utilizing different redundancy versions (RVs).Typically four RVs are defined in LTE Rel-8.

The soft buffer determination is an important element in the HARQoperation, wherein rate matching techniques are used in the receiver ifit has a limited amount of soft buffer size. In LBRM, the transmittermay have knowledge of the soft buffer capability of the receiver andhence it is permitted to transmit no more code bits than can be storedin the receiver's soft buffer. If the rate matching is performed on acodeword-by-codeword (i.e., segment by segment) basis, then the LBRM, ifincluded, may also be performed on a codeword-by-codeword(segment-by-segment) basis as well. Therefore, each segment of the TBmay have its own circular buffer (or virtual circular buffer). It isgenerally not necessary to create physical circular buffers for eachsegment. The circular buffer size for each code word (or segment) islimited to Ncw, where Ncw may be smaller than or equal to the length ofthe full circular buffer size (per-segment) before LBRM. In case theavailable soft buffer memory per segment is larger than the fullcircular buffer size, then the LBRM is transparent. Otherwise, thecircular buffer is shortened and bits that may not be stored by thereceiver may not be transmitted by the transmitter. This is done byeither deleting the bits from the circular buffer and/or by wrappingaround at an earlier point rather than the end of the circular buffer.

While the example in the present description uses turbo coding, the sametechnique for soft buffer and HARQ processing may be applied to othercodes such as LDPC codes, convolutional codes, Reed Solomon codes, ReedMuller codes, etc. The same technique may also be applied to the case ofcarrier segments, wherein a first and second component carriers share atleast one subcarrier. For instance, a first component carrier may beusing a 10 MHz bandwidth and the second component carrier may beoccupying a 20 MHz bandwidth, wherein the second component carriercomprises at least one subcarrier contained in the first subcarrier. Inthis case, a TB can be scheduled in the first component carrier andsubsequently be rescheduled on the second component carrier. Thus, a TBis assigned a soft buffer partition based on the component carrier onwhich the TB is scheduled on the first transmission. Thus, if the TB isfirst scheduled on the first component carrier, it is allocated a softbuffer of length X associated with the first component carrier and if itis retransmitted on the second component carrier, then the soft buffersize for the TB is still assumed to be X. Thus, if the TB was firstscheduled on the second component carrier, it is allocated a soft bufferof length Y associated with the second component carrier and if it isretransmitted on the first component carrier, then the soft buffer sizefor the TB is still assumed to be Y. The value of X may not be equal tothe value of Y.

In some future networks the UE may be also required to enhanceperformance by means of cancelling interference. For example, if the UEknows the characteristics of the interference, it can employ suitablemeans to reduce the impact of the interference. For instance, if a firstUE determines that a downlink transmission meant for a second UE is asource of interference, then the first UE may be able to decode thedownlink transmission (e.g., by decoding the DL grants) meant for thesecond UE and cancel the downlink transmission from the received signalto decode data transmissions meant for the UE. In some embodiments, theUE may choose to or be instructed by the serving cell to set aside somesoft buffer (as well as computing such as turbo decoding) resources forinterference cancellation or for handling interference, in general. Inanother example, if a first UE acts as a relay node to assist theserving eNB to serve a second UE, then the first UE may have limitedsoft buffer and computing resources. Such UE may again choose to, or getinstructed by the eNB to allocate a portion of soft buffer for servingother UEs and use a second portion of the soft buffer for communicatingwith the eNB.

While the present disclosure and the best modes thereof have beendescribed in a manner establishing possession and enabling those ofordinary skill to make and use the same, it will be understood andappreciated that there are equivalents to the exemplary embodimentsdisclosed herein and that modifications and variations may be madethereto without departing from the scope and spirit of the inventions,which are to be limited not by the exemplary embodiments but by theappended claims.

What is claimed is:
 1. A wireless communication device supportingmultiple carriers, the multiple carriers comprising at least twocomponent carriers, each component carrier is associated with aconfigured bandwidth, the apparatus comprising: a receiver; a memoryelement; a processor coupled to the receiver and to the memory element,the processor configured to determine a size of a soft buffer memorypartition of the memory element for a first component carrier based on afirst configured bandwidth of the first component carrier and a secondconfigured bandwidth of a second component carrier, and the processorconfigured to control the receiver to receive data on the firstcomponent carrier based on the size of the soft buffer memory partition.2. The apparatus of claim 1 wherein the processor is configured todetermine the size of the soft buffer memory partition based on a totalnumber of soft channel bits.
 3. The apparatus of claim 1, wherein theprocessor is configured to determine the size of the soft buffer memorypartition based on a maximum number of spatial multiplexing layerssupported on the first component carrier.
 4. The apparatus of claim 1,wherein a ratio of the size of the soft buffer memory partition for thefirst component carrier and a size of the soft buffer memory partitionfor the second component carrier is substantially equal to a ratio ofthe first configured bandwidth of the first component carrier and thesecond configured bandwidth of the second component carrier.
 5. Theapparatus of claim 2, wherein the first configured bandwidth of thefirst component carrier is not equal to the second configured bandwidthof the second component carrier.
 6. The apparatus of claim 1, whereinthe processor is configured to determine the size of the soft buffermemory partition based on a bandwidth corresponding to a signaledcategory of the wireless communication device.
 7. The apparatus of claim1, wherein the processor is configured to re-determine the size of thesoft buffer memory partition for the first component carrier in responseto a change in an activation or a change in a configuration of thesecond component carrier.
 8. The apparatus of claim 1, wherein theprocessor is configured to re-determine the size of the soft buffermemory partition for the first component carrier based on a change in atransmission mode of the second component carrier.
 9. The apparatus ofclaim 1, wherein the processor is configured to determine the size ofthe soft buffer memory partition based on a first number associated withthe hybrid automatic retransmit request process, the first numbercomprises a maximum number of downlink hybrid automatic retransmitrequest processes on the first component carrier.
 10. The apparatus ofclaim 1, wherein the processor is configured to determine the size ofthe soft buffer memory partition based on a second number associatedwith hybrid automatic retransmit request processes, the second numbercomprising a configured maximum number of hybrid automatic retransmitrequest processes on the second component carrier.
 11. The apparatusaccording to claim 2, wherein the total number of soft channel bits isdetermined based on any one of the following: a category of the wirelesscommunication device; a first number associated with hybrid automaticretransmit request processes determined based at least in part on duplexmode; or a maximum number of transport blocks transmittable to thewireless communication device in one transmission time interval.
 12. Themethod of claim 2, wherein the processor is configured to determine thetotal number of soft channel bits based on a second number associatedwith hybrid automatic retransmit request processes determined based atleast in part on a number of Multiple Input Multiple Output streams. 13.A method in a wireless communication device supporting multiplecarriers, the multiple carriers comprising at least two componentcarriers, each component carrier is associated with a correspondingconfigured bandwidth, the method comprising: determining a size of asoft buffer memory partition associated with receiving data on a firstcomponent carrier, the size of the soft buffer memory partitiondetermined based on a first configured bandwidth of a first componentcarrier and a second configured bandwidth of a second component carrier;receiving data on the first component carrier based on the soft buffermemory partition size.
 14. The method of claim 13, wherein the first andsecond component carriers are at least partially non-overlapping. 15.The method of claim 13, determining the size of the soft buffer memorypartition based on either a total number of soft channel bits or a firstnumber associated with hybrid automatic retransmit request processesassociated with the first component carrier.
 16. A method in a wirelesscommunication device supporting multiple carriers, the multiple carrierscomprising at least two component carriers, the method comprising:determining a size of a soft buffer memory partition for a hybridautomatic retransmit request (HARQ) process associated with a firstcomponent carrier of the multiple carriers based on a number of softchannel bits associated with the first component carrier, a maximumnumber of spatial multiplexing layers supported on the first componentcarrier, and a first number associated with the HARQ process associatedwith the first component carrier; and receiving a data transmission onthe first component carrier based on the determined size of the softbuffer memory partition.
 17. The method of claim 16, wherein the size ofthe soft buffer memory partition is based on a second number associatedwith the HARQ process associated with the first component carrier. 18.(canceled)
 19. A wireless communication device supporting multiplecarriers comprising at least two component carriers, wherein eachcomponent carrier is associated with a configured bandwidth, theapparatus comprising: a transceiver; a processor coupled to thetransceiver, the processor configured to determine a size of a softbuffer memory partition for a hybrid automatic retransmit request (HARQ)process associated with a first component carrier of the multiplecarriers based on a number of soft channel bits associated with thefirst component carrier, a maximum number of spatial multiplexing layerssupported on the first component carrier, and a first number associatedwith HARQ process associated with the first component carrier; theprocessor configured for receiving, via the transceiver, a datatransmission on the first component carrier based on the determined sizeof the soft buffer memory partition.
 20. (canceled)